Centrifugal pump with unitary inlet bushing and wear plate



Dec. 23, 1969 K. DUTTON ETAL 3,485,178

CENTRIFUGAL PUMP WITH UNITARY INLET BUSHING AND WEAR PLATE Filed Sept. 1, 196'. 5 Sheets-Sheet l INVENTORS LLOYD K. DUTTON FRANCIS K. LYNCH THEIR ATTOR EYS Dec. 23, 1969 1.. K. DUTTON ETAL 3,485,178

CENTRIFUGAL PUMP WITH UNITARY INLET BUSHING AND WEAR PLATE Filed Sept. 1, 196'. 3 Sheets-Sheet 2 "I 3 INVENTORS LLOYD K. DUTTSN BY FRANCIS K. LYNCH THEIR ATTORNE S Dec. 23, 1969 L. K. DUTTON ETAL 3,485,178

CENTRIFUGAL PUMP WITH UNITARY INLET BUSHING AND WEAR PLATE Filed Sept. 1, 1967 3 Sheets-Sheet 5 mum MIIWHWHHI INVENTORS LLOY BUTTON FRAN K. CH

MW THEIR A OR YS nited States Patent 3,485,178 CENTRH'UGAL PUMP WITH UNITARY INLET BUSHING AND WEAR PLATE Lloyd K. Dutton, West Paterson, and Francis K. Lynch,

Hewitt, N.J., assignors to Mooney Brothers Corporation, Little Falls, N.J., a corporation of New Jersey Filed Sept. 1, 1967, Ser. No. 665,131 Int. Cl. F04d 29/02, 1/00, 29/04 U.S. Cl. 103114 5 Claims ABSTRACT OF THE DISCLOSURE The present invention relates generally to centrifugal pumps and pertains, more specifically, to an inlet bushing construction for use in centrifugal pumps which are employed primarily for pumping corrosive fluids.

The term corrosive fluids is meant to encompass all fluids which should be isolated from those structural components of the pump which are susceptible to some unfavorable reaction With the fluid being pumped, including those fluids which might themselves be contaminated or otherwise degraded by contact with the structural components, such as pure or ultra-pure fluids which must be maintained at a high level of purity.

It is conventional practice in the design and construction of centrifugal pumps to place a bearing surface adjacent the inlet end of the impeller of the pump and, in some instances, a separate plate, known as a wear plate, has been placed between the inlet end of the impeller and the corresponding portion of the pump housing to provide the desired bearing surface. Such wear plates have the advantage of being replaceable whenever necessary to maintain the proper tolerances between the Wear plate and the impeller.

During the operation of such pumps, it has been found that thermal expansion of the various component parts of the pump can cause an axial displacement of the wear plate relative to the impeller, such axial displacement being permitted as a result of the clearance which must be provided between the confronting surfaces of the Wear plate and the impeller to preclude constant rubbing contact between these confronting surfaces.

In those centrifugal pumps which are constructed for handling corrosive fluids, the surfaces of the component parts of the pump which come into contact with the fluid being pumped are advantageously constructed of materials which can withstand the corrosive eifects of the fluid. Thus, the pump chamber within the pump housing is often lined with corrosion resistant materials, such as glass, or another ceramic, or a corrosion resistant synthetic resin, and the impeller can likewise be fabricated of a corrosion resistant material. However, a problem arises in providing a wear plate of corrosion resistant material which can be both properly secured in place within the pump chamber and which can also be displaced as a result of thermal expansion without deleterious effects on either the integn'ty of the wear plate or the corrosion resistant internal structure of the pump.

3,435,178 Patented Dec. 23, 1969 It is therefore an important object of the invention to provide, in a centrifugal pump which is capable of pumping corrosive fluids, a wear plate which is corrosion resistant and which will not disturb the corrosion resistant internal structure of the pump during normal operation of the pump.

Another object of the invention is to provide, in a centrifugal pump, a Wear plate constructed of a material having a low coefficient of friction as well as good corrosion resistance and suflicient structural strength to withstand service within the pumping chamber of the pump.

Still another object of the invention is to provide a wear plate as described above and which is a part of a unitary inlet bushing having a construction which allows compensation for thermal expansion during use without failure of the inlet bushing or the corrosion resistant structure of the pump.

A further object of the invention is to provide a wear plate which is an integral part of an inlet bushing, the construction of which allows ease of assembly within the pump and ease of replacement.

The above objects, as well as further objects and advantages are attained by the invention which may be described briefly as an inlet bushing in a centrifugal pump capable of pumping corrosive fluids and having a pump chamber with internal surfaces of corrosion-resistant materials, the pump chamber including a pump casing and an inlet flange assembly aflixed thereto and having an inlet passage passing axially therethrough, an impeller within the pump chamber and the inlet bushing located between the impeller and the inlet flange assembly, the inlet bushing comprising a unitary body of a fluorocarbon synthetic resin material and including an annular wear-plate portion of relatively large axial length extending between a front face juxtaposed with the inlet flange assembly and a rear face juxtaposed with the impeller to establish a relatively thick wear plate between the inlet flange assembly and the impeller, the annular wear-plate portion having an inside diameter corresponding to the diameter of the inlet passage and an outside diameter corresponding to the inside diameter of the pump casing, an annular flange portion coextensive with the front face and projecting radially outwardly beyond the outside diameter of the Wearplate portion, the flange portion having a relatively small axial length in order to present a relatively thin outer annular flange part between the inlet flange assembly and the pump casing for retaining the inlet bushing in place within the pump chamber and sealing the juncture between the inlet flange assembly and the pump casing, and an annular groove between the annular flange portion and the wear-plate portion and extending radially into the body thereby extending the annular flange portion radially inwardly beyond the outside diameter of the wear-plate portion to establish a relatively flexible inner annular part in the annular flange portion between the inside diameter of the annular flange portion and the inside diameter of the pump casing for permitting axial displacement of the wear-plate portion relative to the outer annular flange part without disturbing the seal between the inlet flange assembly and the pump casing. The fluorocarbon synthetic resin material is preferably polytetrafiuoroethylene,

The invention will be more fully understood and still further objects and advantages will become apparent in the following detailed description of an embodiment of the invention illustrated in the accompanying drawing, in which:

FIGURE 1 is a side elevational view, partially sectioned, of a centrifugal pump employing an inlet bushing as contemplated in the invention;

FIGURE 2 is an enlarged cross-sectional view of a portion of FIGURE 1;

FIGURE 3 is a front elevational view of the centrifugal pump sectioned along line 3-3 of FIGURE 2; and

FIGURE 4 is a perspective view of an inlet bushing constructed in accordance with the invention.

Referring now to the drawing, FIGURE 1 illustrates a centrifugal pump in which a pump housing 12 is affixed to a bearing block 14 in which is supported a drive shaft 16. An impeller 18 is integral with the drive shaft 16 and rotates therewith within the pump chamber 20 of the pump housing 12 such that the fluid being pumped will enter the pump at an inlet 22 and leave the pump at an outlet 24.

The pump housing 12 is an assembly which includes a generally cylindrical pump casing 26 having a front end 27 and a rear end 28. An inlet flange assembly 30 is placed against the front end 27 of the pump casing 26 while a rear flange assembly 32 is placed against the rear end 28 of the pump casing.

A back-up plate 34 is affixed to the bearing block 14 by cap screws 36 (only one of which is shown) passing through corresponding spacers 38 and threaded into the back-up plate 34 to which is attached a coolant casing 40. The coolant casing 40 is held in place upon the backup plate 34 by means of four cap screws 41 (only three of which are illustrated). A drive shaft seal assembly 42 is supported by the back-up plate 34 and engages the rear flange assembly 32 at an aperture 44 in the rear flange assembly. Four cap screws 46 (only one of which is shown in FIGURE 1) pass through the inlet flange assembly 30 and the rear flange assembly 32 and are threaded into the back-up plate 34 such that upon tightening of the cap screws 46, the rear flange assembly will be firmly seated upon the shaft seal assembly 42 and both the inlet flange assembly 30 and the rear flange assembly 32 will be seated and sealed against the corresponding ends of the pump casing 26 to establish a sealed pump chamber in the pump housing. An inlet passage 48 passes axially through the inlet flange assembly 30 to communicate with the pump chamber 20.

Centrifugal pump 10 is especially constructed to pump corrosive fluids. Thus, those component parts which will contatin the fluid which passes through the pump and which have surfaces that will contact such corrosive fluids are protected by corrosion-resistant means. As best seen in FIGURES 2 and 3, these means are shown in the form of a lining 50, preferably fabricated of glass, which lines the internal portions of the pump casing 26 and has an internal surface 52, defined by an internal diameter, which is resistant to corrosion or to any other deleterious reaction with the fluid in the pump chamber. The inlet flange assembly 30 is provided with an envelope 54 which is fabricated of a corrosion-resistant material and includes an axially extending sleeve portion 56, establishing a corrosion-resistant surface for inlet passage 48, and integral radially extending flange portions 58 and 59. The flange portions 58 and 59 are backed up by first and second filler pieces 60 and 62, respectively, which filler pieces are constructed of a resilient material to allow the flange portions to be urged against the ring portion 64 of the inlet flange assembly, which ring portion is preferably fabricated of a relatively rigid material such as steel, to establish a seal. Thus, a plurality of studs 66 are anchored within the ring portion 64 and carry nuts 68 for securing an inlet fitting (not shown) upon the inlet flange assembly 30 and against the flange portion 58 of the envelope 54 where the fitting is sealed in communication with the inlet passage 48. Envelope 54 is fabricated of a corrosion-resistant material which is flexible and which will establish the desired seal, a preferable material being a fluorocarbon synthetic resin, such as polytetrafluoroethylene.

Turning back to FIGURE 1, the rear flange assembly 32 is likewise provided with an envelope 70 of corsion-resistant material, such as polytetrafluoroethylene, en-

velope 70 also having a sleeve portion 72, providing a corrosion-resistant surface for aperture 44, and integral flange portions 74 and 76 which are backed up by first and second filler pieces 78 and 79, respectively. Flange portion 74 is urged against the shaft seal assembly 42, which is also formed of a corrosion-resistant material, to establish a seal between the aperture 44 and the shaft seal assembly.

Returning now to FIGURE 2, located between the inlet flange assembly 30 and the impeller 18 is an inlet bushing 80 which extends axially from a front face 82 juxtaposed with the inlet flange assembly to a rear face 84 juxtaposed with the impeller to establish a relatively thick wear-plate portion 86. As best seen in FIGURES 3 and 4, inlet bushing 80 is annular and has an outside diameter corresponding to the inside diameter of the pump casing 26 and an inside diameter corresponding to the diameter of inlet passage 48 for providing a bore 88 leading from the inlet passage to the eye of the impeller. In order to aflix the wear-plate portion in place within the pump chamber 20, the inlet bushing 80 is provided with an annular flange portion 90 which is coextensive with the front face 82 and extends radially outwardly beyond the outside diameter of the wear-plate portion 86 to establish an outer annular flange part 91 which fits between the front end 27 of the pump casing 26 and the flange portion 59 of the envelope 54 in the inlet flange assembly 30 in clamped arrangement.

The inlet bushing 80 is constructed in the form of a unitary body of corrosion-resistant material such as fluorocarbon synthetic resin and is preferably fabricated of polytetrafluoroethylene. The annular part 91 of the annular flange portion 90 is relatively thin and establishes an effective seal between the front end of the pump casing and the inlet flange assembly while maintaining the integrity of the corrosion-resistant interior surfaces of the pump housing.

During operation of the pump, thermal expansion of the various pump component parts of different materials will take place in varying amounts. Primarily, the armored glass construction of the pump casing will undergo a different amount of thermal expansion than the inlet flange assembly and the inlet bushing, thereby placing a stress upon the inlet bushing which will tend to shear the relatively thin annular flange portion of the inlet bushing from the relatively thick wear-plate portion. In order to avoid such shearing, the body of the inlet bushing is provided with an annular groove 92 between the annular flange portion 90 and the wear-plate portion 86, the annular groove 92 extending radially inwardly into the body of the inlet bushing to extend the annular flange portion radially inwardly and establish a relatively flexible inner annular part 94 of sufficient radial extent to permit axial movement of the wear-plate portion 86 relative to the clamped outer annular part 91 with a flexing of the inner annular part 94 rather than failure of the annular flange portion 90 and without disturbing the seal between the inlet flange assembly and the pump casing. Thus, the inlet bushing is readily placed in assembled position in the pump housing and is retained in place against adverse stresses, while a simple and effective, readily replaceable configuration is maintained.

Additionally, although it is desirable to establish a sufficient amount of clearance between the rear face 84 of the inlet bushing 80 and the end of the impeller 18, the clearance should be small and, as a result, the impeller will sometimes contact the rear face 84 during operation of the pump. For this reason, it is advantageous that the inlet bushing, and particularly the rear face thereof which may contact the im eller, have a relatively low coefficient of friction. By fabricating the inlet bushing of a fluorocarbon resin, a low coeflicient of friction is attained.

It is to be understood that the above detailed description of the invention is provided by way of example only. Various details of design and construction may be modified without departing from the true spirit and scope of the invention as set forth in the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a centrifugal pump capable of pumping corrosive fluids and having a pump chamber with internal surfaces of corrosion-resistant materials, the pump chamber including a pump casing and an inlet flange assembly aflixed thereto and having an inlet passage passing axially there through, an impeller within the pump chamber and an inlet bushing located between the impeller and the inlet flange assembly, said inlet bushing comprising a unitary body of a fluorocarbon synthetic resin material and including:

an annular wear-plate portion of relatively large axial length extending between a front face juxtaposed with the inlet flange assembly and a rear face juxtaposed with the impeller to establish a relatively thick Wear plate between the inlet flange assembly and the impeller, said annular wear-plate portion having an inside diameter corresponding to the diameter of the inlet passage and an outside diameter corresponding to the inside diameter of the pump casing;

an annular flange portion coextensive with said front face and projecting radially outwardly beyond the outside diameter of said wear-plate portion, said flange portion having a relatively small axial length in order to present a relatively thin outer annular flange part between the inlet flange assembly and the pump casing for retaining the inlet bushing in place within the pump chamber and sealing the juncture between the inlet flange assembly and the pump casing; and

an annular groove between the annular flange portion and the wear-plate portion and extending radially into the body thereby extending the annular flange portion radially inwardly beyond the outside diameter of the wear-plate portion to establish a relatively flexible inner annular part in the annular flange portion between the inside diameter of the annular flange portion and the inside diameter of the pump casing for permitting axial displacement of the wearplate portion relative to the outer annular flange part Without disturbing the seal between the inlet flange. assembly and the pump casing.

2. The invention of claim 1 wherein the fluorocarbon synthetic resin is polytetrafluoroethylene.

3. A centrifugal pump construction comprising:

a pump casing having an interior and extending axially from a front end to a rear end;

an impeller aligned axially within the interior of the pump casing;

an inlet flange assembly aflixed to the pump casing at a relatively thick inlet bushing of a fluorocarbon synthetic resin material lying within the pump casing between the impeller and the inlet flange assembly, said inlet bushing having an outside diameter and including a radially extending face. juxtaposed with the impeller, an axially extending opening leading from the inlet passage to the impeller, a relatively thin annular flange juxtaposed with the inlet flange assembly and extending radially outwardly beyond said outside diameter between the inlet flange assembly and the front end of the pump casing and held aflixed therebetween, and an annular groove extending radially inwardly along the. annular flange and between the annular flange and said radially extending face thereby extending the relatively thin annular flange radially inwardly beyond the outside diameter of the inlet bushing. 4. The centrifugal pump of claim 3 including: first corrosion-resistant means lining the interior of the pump casing; and second corrosion-resistant means lining the interior surface and the inlet passage of the inlet flange assembly; said relatively thin annular flange establishing a seal between said first and second corrosion-resistant means. 5. The centrifugal pump of claim 4 wherein said fluorocarbon material is polytetrafluoroethylene.

References Cited UNITED STATES PATENTS HENRY F. RADUAZO, Primary Examiner US. Cl. X.R. 

